In recent years, the demand for low fuel consumption of automobiles is increasing more and more. Therefore, there is a growing need for early warming up technology to reduce the frictional resistance during cold by warming up the engine and the transmission early.
That is, promoting the warm-up of both the engine and the transmission leads to an improvement in fuel economy. Warming up of the engine and the transmission is performed using heat generated from the engine as a heat source.
On the other hand, as the size of the engine becomes smaller and the hybrid vehicle becomes common, the amount of heat generated from the engine is getting smaller, and the time required for warm-up tends to become longer.